Seal ring

ABSTRACT

A seal ring which maintains a stable sealing performance over a long term is provided. In a first seal portion, linear contact portions which come into linear contact with the sidewall surface of an annular groove on the unsealed fluid side are continuously extended over the whole circumference of the seal ring from one side of a separation portion to the other side thereof, and the linear contact part provided at the convex part of the separation portion, and the linear contact part provided at the concave part of the separation portion are located at a distance in the radial direction of the seal ring.

This is a nationalization of PCT/JP03/09469 filed Jul. 25, 2003 andpublished in Japanese.

TECHNICAL FIELD

This invention relates to a seal ring for sealing the annular interspacebetween two members which are disposed so as to be rotatable relative toeach other.

BACKGROUND ART

Heretofore, a seal ring of this type has been employed in hydraulicdevices, for example, the automatic transmission of an automobile.

Now, a seal ring according to a prior-art technique will be explainedwith reference to FIGS. 34 and 35.

FIG. 34 is a planar model view of the seal ring according to theprior-art technique, while FIG. 35 is a model-like sectional viewshowing the mounted state of the seal ring according to the prior-arttechnique.

The illustrated seal ring 100 serves to seal the annular interspacebetween a housing 200 provided with a shaft hole and a shaft 300inserted in the shaft hole, and it is used in a state where it ismounted within an annular groove 301 provided in the shaft 300.

The seal ring 100 is formed of a resin material, and it includes a firstseal portion 101 for sealing the sidewall surface of the annular groove301 provided in the shaft 300, and a second seal portion 102 for sealingthe inner peripheral surface of the shaft hole provided in the housing200.

Herein, when a pressure acts in the direction of an arrow P in FIG. 35,from the sealed fluid side O toward the unsealed fluid side A, the sealring 100 is urged onto the unsealed fluid side A, and hence, the firstseal portion 101 urges the sidewall surface of the annular groove 301,while the second seal portion 102 urges the inner peripheral surface ofthe shaft hole provided in the housing 200 and opposing to the annulargroove 301, so as to seal the surfaces at the positions of therespective seal portions.

In this way, the sealed fluid has been prevented from leaking onto theunsealed fluid side A.

Here, the sealed fluid is, for example, lubricating oil, and itsignifies ATF especially in a case where the seal ring is utilized forthe automatic transmission of an automobile.

Besides, as shown in FIG. 34, the ring body of the seal ring 100 isprovided with a separation portion So at one part in the circumferentialdirection thereof for the purposes of enhancing an assemblability, etc.

Various aspects have been known as such a separation portion So, and aspecial step cut in the shape of two steps has been known as an aspectcapable of suitably coping even with the change of an ambienttemperature.

According to the special step cut, the wall surfaces of the ring body inthe circumferential direction thereof come into close contact with eachother, so that the sealed fluid can be prevented from leaking. Moreover,owing to a construction wherein the seal ring cuts off the sealed fluidside and the unsealed fluid side while the surfaces of the ring bodyperpendicular to the circumferential direction define gaps in thecircumferential direction therebetween, even when the seal ring hasrelatively moved in the circumferential direction on account of thediscrepancy of the coefficients of linear expansion attributed to thedifferent materials of the seal ring and the housing, the variations ofdimensions can be absorbed in correspondence with the gaps while atightly enclosing state is kept, so that the seal ring can suitablymaintain a tightly enclosing performance even against the ambienttemperature change.

In such a seal ring 100, especially in a case where the shaft 300 is ofan aluminum alloy or the like soft material, especially the sidewallsurface of the annular groove 301 has worn away on account of the slidebetween the first seal portion 101 and the sidewall surface of theannular groove 301, which is ascribable to the relative rotation betweenthe seal ring 100 and the shaft 300.

This is because a lubricating film based on the lubricating oil isdifficult to be formed between the first seal portion 101 and thesidewall surface of the annular groove 301. Especially in a case whereany foreign matter existent in the lubricating oil has been bittenbetween the first seal portion and the sidewall surface, or where theaccumulation of wear powder, or the like has occurred, the wear becomesintense. Also, in a case where the seal ring 100 has been used under ahigh pressure and at a high rotational speed, the first seal portion 101and the sidewall surface of the annular groove 301 become a hightemperature on account of the relative rotation between the seal ring100 and the shaft 300, and the seal ring 100 is sometimes molten.

As a technique for reducing such wear, there has been known one whereina slot which serves to feed the lubricating oil being the sealed fluidbetween the first seal portion 101 and the sidewall surface of theannular groove 301 is provided, thereby to form a lubricating film andto enhance a wear-proofness (for example, JP-A-9-96363).

FIG. 36 shows model diagrams of a seal ring according to a prior-arttechnique, wherein FIG. 36A is a model-like partial plan view, FIG. 36Bis a sectional view taken along b-b in FIG. 36A, and FIG. 36C is a sideview seen in an I-direction in FIG. 36A.

As shown in FIG. 36, the first seal portion 101 is provided with thecommunicating slot 101 a for communicating the sealed fluid side O withthe unsealed fluid side A, whereby the lubricating oil on the sealedfluid side O is caused to leak into the communicating slot 101 a. Thus,when the first seal portion 101 has come into sliding contact with thesidewall surface of the annular groove 301, the lubricating film isformed between them, to improve the lubricating state of the sealsurface and to attain enhancement in the wear-proofness.

Besides, the provision of the communicating slot 101 a, not only formsthe lubricating film, but also affords the function of vomiting theforeign matter existent in the lubricating oil and the wear powderascribable to the wear, onto the unsealed fluid side A so as not to bebitten between the first seal portion 101 and the sidewall surface ofthe annular groove 301, and it cools the seal surface owing to theformation of the lubricating film, thereby to attain the enhancement ofthe wear-proofness still more.

Even with the seal ring according to the prior-art technique asexplained above, however, the occurrence of the wear of the sidewallsurface of the annular groove 301 is often found. As the result of astudy by the Inventor, it has been revealed that the sidewall surface ofthe soft metal wears away because the foreign matter existent in thelubricating oil intervenes between the sliding surfaces.

Besides, in a case where the wear has proceeded due to a long-term use,the sidewall surface of the annular groove 301 wears away only at itspart with which the first seal portion 101 is brought into slidingcontact, as shown in FIG. 37, so that the seal ring 100 is pushedinwards with respect to the original position of the sidewall surface ofthe annular groove 301 in correspondence with a component having worn.

In addition, when the bottom surface of the communicating slot 101 a hasreached that plane of the sidewall surface of the annular groove 301which is not worn, a path leading to the communicating slot 101 a is cutoff as indicated by an arrow X in FIG. 37, and the lubricating oil failsto be fed, so that the drawback of the occurrence of abnormal wear mighttake place.

In this regard, there has also been known a seal ring 400 whosesectional shape is trapezoidal as shown in FIGS. 38 and 39. The sealring 400 has been constructed for the purpose that a seal portion 402comes into linear contact in order to reduce sliding friction, and theseal portion 402 is formed at the upper end edge of the annular groove301.

In case of the seal ring 400, leakage occurs through the gap Z between aconvex part and a concave part in the special step cut, irrespective ofwhether or not the sidewall surface of the annular groove inclines.Another problem is that, since the quantity of leakage changes dependingupon the inclination angle of the annular groove, a stable leakagecharacteristic is not obtained.

Besides, in a case where the soft metal is applied to the shaft in thisseal ring, the quantity of wear of the side surface of the shaft grooveis small, but the quantity of leakage thereat changes depending upon agap To. The gap To=width of about 0.2-0.6 mm holds depending upon thedimensional tolerance of the outside diameter of the seal ring and thatof the hole diameter of the housing, and the quantity of leakage in thatcase can become about 200-500 cc/min (0.2-0.5 l/min).

The quantity of leakage of the seal ring which has the separationportion of the general special step cut is at most 100 cc/min (0.1l/min). In such a case as stated above, the quantity of leakage isexcessive and is therefore difficult to be coped with by the ordinarycapacity of a hydraulic pump.

Besides, even when the quantity of leakage is coped with by enlargingthe hydraulic pump capacity in such a case, a loss developing in thehydraulic pump increases. That is, there occurs the problem that a fuelcost degrades.

The present invention has been made in order to solve the problems ofthe prior-art techniques, and has for its object to provide a seal ringof excellent quality which attains reduction in the quantity of leakagewhile reducing rotational sliding friction, and which maintains a stablesealing performance over a long term.

DISCLOSURE OF THE INVENTION

The present invention consists in:

a seal ring including a first seal portion which seals a sidewallsurface of an annular groove on a unsealed fluid side, the annulargroove being provided in one of two members that are concentricallyassembled so as to be relatively rotatable; and

a second seal portion which seals a surface of the other of the twomembers;

wherein an annular interspace between the two members is sealed by theseal portions; and

a ring body of the seal ring is provided with a separation portion whichis separated in one place in a circumferential direction of the sealring;

characterized in that the first seal portion is provided with linearcontact portions which come into linear contact with the sidewallsurface of the annular groove on the unsealed fluid side, so as toextend continuously over a whole circumference of the seal ring from oneside of separation portion to the other side thereof; and

that the linear contact portion which is provided on one side of theseparation portion, and the linear contact portion which is provided onthe other side of the separation portion are located at a distance in adiametric direction of the seal ring.

Since the first seal portion is made the linear contact portions whichcome into linear contact with the sidewall surface of the annular grooveon the unsealed fluid side, the pressure receiving area of a slidingpart can be decreased. Accordingly, the formation of a lubricating filmbased on lubricating oil can be made favorable, and the reduction ofrotational sliding friction can be attained. Besides, even if anyforeign matter has entered the sliding part, it can be easily vomited.

Further, it is permitted to control the quantity of leakage of a sealedfluid by the size of a gap which is formed owing to the fact that thelinear contact portions are provided at the diametric distance in theseparation portion.

Here, the “gap which is formed owing to the fact that the linear contactportions are provided at the diametric distance in the separationportion” signifies a space which is formed by the linear contact portionprovided on one side of the separation portion, the linear contactportion provided on the other side, the side surface of the ring body aslies between the linear contact portion on one side and the linearcontact portion on the other side. The quantity of leakage can beadjusted by adjusting the size of the sectional area of the section ofthe space in the diametric direction.

In order to form the space, the linear contact portion provided on oneside of the separation portion, and the linear contact portion providedon the other side thereof have regions which are placed one over theother when the linear contact portions are projected in the diametricdirection.

The regions which are placed one over the other when the linear contactportions are projected in the diametric direction, is set at apredetermined length in the circumferential direction, whereby the spacecan be made columnar, that is, a leakage path becomes columnar, and theoil passing resistance of the leakage path can be enlarged. Accordingly,the quantity of leakage can be suppressed more.

Further, the quantity of leakage can be controlled by adjusting thecircumferential length of those regions of the linear contact portionprovided on one side of the separation portion and the linear contactportion provided on the other side thereof which are placed one over theother when the linear contact portions are projected in the diametricdirection.

Besides, even in a case where the linear contact portions do not havethe regions which are placed one over the other when these linearcontact portions are projected in the diametric direction, that is,where the linear contact portions are not extended to separation endparts in the circumferential direction, in the separation portion,respectively, a space is formed to form a leakage path, as long as thelinear contact portions on one side and the other side of the separationportion are at a distance in the diametric direction, so that thequantity of leakage can be adjusted.

Besides, it is suitable that the linear contact portions definesubstantially mountain shaped portions which protrude from a sidesurface of the seal ring body, toward the sidewall surface of theannular groove on the unsealed fluid side. Incidentally, the “seal ringbody” includes the separation portion. Here, the expression “linearcontact” will be explained. The linear contact portions run in anelongate line to the sidewall surface of the annular groove on theunsealed fluid side. Therefore, the expression “linear contact” is used,and the linear contact portions have slight widths. Actually, in thecase where the linear contact portions lie in contact with the sidewallsurface of the annular groove on the unsealed fluid side, they liecontact at surfaces having the slight widths (the linear contactportions are sometimes endowed with slight widths). The expression“linear contact”, however, is used in order to distinguish the inventionfrom the case where the whole side surface of the ring body lie incontact as in the prior art.

Besides, it is suitable that the linear contact portion provided on oneside of the separation portion is located nearer a side of the othermember than the linear contact portion provided on the other side of theseparation portion, and that one member mentioned above is assembled soas to rotate from the other side of the separation portion toward oneside mentioned above, through separation end parts which is end parts ofthe separation portion.

Thus, the direction of the leakage path formed between the linearcontact portions on one side and the other side of the separationportions, and the rotating direction of one member can be set at reversedirections. The “fact that the direction of the leakage path and therotating direction of one member are the reverse directions” signifiesthat, on the other member side of the ring body, an opening which isformed by the linear contact portions on one side and the other side ofthe separation portion is opposite into the rotating direction of onemember.

Accordingly, the foreign matter existing in the sealed fluid can beprevented from being fed in between the linear contact portions in theseparation portion, and it can be prevented from intervening between thegap of the linear contact portions and the sidewall surface of theannular groove of one member, so that the wear of the sidewall surfacebecomes preventable.

In this case, it is also suitable that, on the other member side of thering body, the separation end part of one side mentioned above which isprovided with the linear contact portion is provided with a firstcircularly-arcuate protrusive part which protrudes in thecircumferential direction, while the separation end part of the otherside is provided with a first circularly-arcuate recessed part which isfitted with the first circularly-arcuate protrusive part, and that thefirst circularly-arcuate protrusive part is provided with a secondcircularly-arcuate protrusive part which protrudes in thecircumferential direction, while the first circularly-arcuate recessedpart is provided with a second circularly-arcuate recessed part which isfitted with the second circularly-arcuate protrusive part.

Here, it is meant that the first circularly-arcuate protrusive part isprovided at the separation end part of one side mentioned above, in thecase where one member mentioned above is assembled so as to rotate fromthe other side of the separation portion toward one side mentionedabove, through the separation end part.

Thus, the separation portion can be endowed with a directivity, and itis therefore permitted to efficiently perform the job of mounting theseal ring in accordance with the rotating direction of one membermentioned above.

Besides, it is favorable that the linear contact portion is extended tothe second circularly-arcuate protrusive part.

It is also suitable that the separation end part of one side asmentioned above, of the separation portion is provided with acircularly-arcuate protrusive part which protrudes in thecircumferential direction, while the separation end part of the otherside of the separation portion is provided with a circularly-arcuaterecessed part which is fitted with the circularly-arcuate protrusivepart, and that one of respective fitting surfaces at which thecircularly-arcuate protrusive part and the circularly-arcuate recessedpart are fitted is provided with a protrusion which comes into linearcontact with the other surface.

Thus, even if the foreign matter existing in the sealed fluid hasintruded into the separation portion, the protrusion lying in linearcontact does not bite the foreign matter. Even if the foreign matter hasbeen bitten, it is bitten between the parts lying in linear contact, andhence, it is easily vomited (a bite state is easily released). In thiscase, the shape of the protrusion should favorably be, for example, asubstantially wedge-like sectional shape whose thickness decreasesgradually toward the other surface.

Accordingly, even if the foreign matter existing in the sealed fluid hasentered the separation portion, it is not bitten in the separationportion, and it is permitted to prevent the wear of the fitting surfacesfrom occurring. It is also permitted to prevent the wear of the sidewallsurface from occurring due to the fact that the foreign matter is bitteninto the separation portion.

Here, the protrusion which comes into linear contact with the othersurface may be provided at only one of the respective fitting surfacesat which the circularly-arcuate protrusive part and thecircularly-arcuate recessed part are fitted, and such protrusions maywell be provided at the respective fitting surfaces.

It is also suitable that the fitting surfaces are surfaces which aresubstantially perpendicular to the axis of the seal ring, and whichextend in the circumferential direction.

Besides, it is suitable that the linear contact portions include:

a first linear contact portion which is extended continuously from oneside of the separation portion to the other side thereof, and whichcomes into linear contact with the sidewall surface of the annulargroove on the unsealed fluid side; and

a second linear contact portion which lies nearer a groove bottom sideof the annular groove than the first linear contact portion, which isextended continuously from one side of the separation portion to theother side thereof, and which comes into linear contact with thesidewall surface of the annular groove on the unsealed fluid side;

wherein the linear contact portion provided on one side of theseparation portion is the first linear contact portion, while the linearcontact portion provided on the other side of the separation portion isthe second linear contact portion.

A special step cut or a step cut can be mentioned as an example of theseparation portion (dagger shape) as stated above.

Here, the “special step cut” is a separation structure in which two sealsurfaces in the seal ring are both formed with stepped separation parts.Herein, the separation portion includes separation surfaces which extendin the circumferential direction, and the separation end edges of whichare formed as parts of the stepped separation parts at the seal surfacesfor the sidewall surface side of the annular groove on the unsealedfluid side.

On the other hand, the “step cut” is a separation structure in which astepped separation part is formed on the seal surface side of two sealsurfaces in the seal ring, for the sidewall surface side of the annulargroove on the unsealed fluid side. Herein, the separation portionincludes a separation surface which extends in the circumferentialdirection, and the separation end edge of which is formed as part of thestepped separation part.

Besides, the expression “two members which are concentrically assembledso as to be relatively rotatable” signifies, for example, a housingwhich is provided with a shaft hole, and a shaft which is inserted inthe shaft hole. Herein, the annular groove is provided in either of thehousing and the shaft, but such annular grooves may well be provided inboth of them.

Incidentally, the above constructional features can be adopted incombination as far as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a seal ring according to the first embodimentof the present invention;

FIG. 2 is a perspective view, partly broken away, showing the mountedstate of the seal ring according to the first embodiment of theinvention;

FIG. 3 is a sectional view of the seal ring taken along 3-3 indicated inFIG. 1;

FIG. 4 is a sectional view of the seal ring taken along 4-4 indicated inFIG. 1;

FIG. 5 is an enlarged view of a part C in FIG. 4;

FIG. 6 is a plan view showing a modification to the seal ring accordingto the first embodiment of the invention;

FIG. 7 is a sectional view of the seal ring taken along 7-7 indicated inFIG. 6;

FIG. 8 is a sectional view of the seal ring taken along 8-8 indicated inFIG. 6;

FIG. 9 is a perspective view, partly broken away, showing the mountedstate of a seal ring according to the second embodiment of theinvention;

FIG. 10 is a sectional view of a separation portion (corresponding tothe section 3-3 of the seal ring shown in FIG. 1);

FIG. 11 is a sectional view corresponding to the section 4-4 of the sealring shown in FIG. 1;

FIG. 12 is an enlarged view of a part H in FIG. 11;

FIG. 13 is a schematic view for explaining problems, in the thirdembodiment of the invention;

FIG. 14 is a perspective view, partly broken away, showing the mountedstate of a seal ring according to the third embodiment of the invention;

FIG. 15 is a perspective view, partly broken away, showing the spacedstate of a separation portion in order to explain the construction ofthe separation portion of the seal ring according to the thirdembodiment of the invention;

FIG. 16 is a perspective view, partly broken away, showing the mountedstate of a seal ring according to the fourth embodiment of theinvention;

FIG. 17 is a perspective view, partly broken away, showing the spacedstate of a separation portion in order to explain the construction ofthe separation portion of the seal ring according to the fourthembodiment of the invention;

FIG. 18 is a schematic view showing an example of an endurance testequipment;

FIG. 19 is a schematic view for explaining problems, in the fifthembodiment of the invention;

FIG. 20 is a perspective view, partly broken away, showing the mountedstate of a seal ring according to the fifth embodiment of the invention;

FIG. 21 is a perspective view, partly broken away, showing the spacedstate of a separation portion in order to explain the construction ofthe separation portion of the seal ring according to the fifthembodiment of the invention;

FIG. 22 is a sectional view of the separation portion (corresponding tothe section 3-3 of the seal ring shown in FIG. 1);

FIG. 23 is a top view, partly broken away, showing the mounted state ofthe seal ring according to the fifth embodiment of the invention;

FIG. 24 is an enlarged view of the part W of the seal ring as indicatedin FIG. 23;

FIG. 25 is a perspective view, partly broken away, showing a case wherea lip part is provided in one place, in the fifth embodiment of theinvention;

FIG. 26 is a top view, partly broken away, showing the case where thelip part is provided in one place, in the fifth embodiment of theinvention;

FIG. 27 is a perspective view, partly broken away, showing the mountedstate of a seal ring according to the sixth embodiment of the invention;

FIG. 28 is a perspective view, partly broken away, showing the spacedstate of a separation portion in order to explain the construction ofthe separation portion of the seal ring according to the sixthembodiment of the invention;

FIG. 29 is a sectional view of the separation portion (corresponding tothe section 3-3 of the seal ring shown in FIG. 1);

FIG. 30 is a plan view of a seal ring according to the seventhembodiment of the invention;

FIG. 31 is a perspective view, partly broken away, showing the mountedstate of the seal ring according to the seventh embodiment of theinvention;

FIG. 32 is a sectional view taken along the section 32-32 of the sealring as indicated in FIG. 30;

FIG. 33 is a sectional view taken along the section 33-33 of the sealring as indicated in FIG. 30;

FIG. 34 is a view showing a seal ring according to a prior-arttechnique;

FIG. 35 is a view showing the seal ring according to the prior-arttechnique;

FIG. 36 is a view showing a seal ring according to a prior-arttechnique;

FIG. 37 is a view showing the seal ring according to the prior-arttechnique;

FIG. 38 is a view showing a seal ring according to a prior-arttechnique; and

FIG. 39 is a view showing the seal ring according to the prior-arttechnique.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

A seal ring 1 according to the first embodiment of the present inventionwill be described with reference to FIG. 1-FIG. 5. FIG. 1 is a plan viewof the seal ring 1 according to the first embodiment of the invention,FIG. 2 is a perspective view, partly broken away, showing the mountedstate of the seal ring 1 according to this embodiment, FIG. 3 is asectional view of the seal ring 1 taken along 3-3 indicated in FIG. 1,FIG. 4 is a sectional view of the seal ring 1 taken along 4-4 indicatedin FIG. 1, and FIG. 5 is an enlarged view of a part C in FIG. 4.

The seal ring 1 serves to seal the annular interspace between a shaft 70which is one member inserted in a shaft hole and a housing 80 which isthe other member provided with the shaft hole, and it is used in a statewhere it is mounted within an annular groove 71 provided in the shaft70.

Besides, the seal ring 1 is formed of a resin material, and it includesa first seal portion 4 for sealing the sidewall surface 72 of theunsealed fluid side A in the annular groove 71 provided in the shaft 70,and a second seal portion 3 for sealing the inner peripheral surface 81of the shaft hole provided in the housing 80.

Herein, when a pressure acts in the direction of an arrow P in FIG. 3,from the sealed fluid side O toward the unsealed fluid side A, the sealring 1 is urged onto the unsealed fluid side A, and hence, the firstseal portion 4 urges the sidewall surface 72 of the annular groove 71,while the second seal portion 3 urges the inner peripheral surface 81 ofthe shaft opposing to the annular groove 71, so as to seal the surfacesat the positions of the respective seal portions.

In this way, the sealed fluid is prevented from leaking onto theunsealed fluid side A.

Here, the sealed fluid is, for example, lubricating oil, and itsignifies ATF especially in a case where the seal ring is utilized forthe transmission of an automobile.

Besides, as shown in the figures, the ring body of the seal ring 1 isprovided with separation portions 2 at one part in the circumferentialdirection thereof for the purposes of enhancing an assemblability, etc.

Various aspects have been known as such separation portions 2, and aspecial step cut in the shape of two steps as shown in the figures hasbeen adopted in this embodiment, as an aspect in which the quantity ofleakage is small and which can suitably cope even with the change of anambient temperature. More specifically, as shown in the figures, thestepped separation portions are formed on both the side of the firstseal portion 4 and the side of the second seal portion 3.

The special step cut includes a convex part 21 and a concave part 22 ina widthwise (axial direction) pair, on one side of the outer peripheralside of the ring body through a separated part, and a concave part 24and a convex part 23 in a widthwise pair, also on the other side.Besides, it is constructed so that the convex part 21 and the concavepart 24 may be fitted, while the concave part 22 and the convex part 23may be fitted.

According to the construction of the special step cut, the sealed fluidside O and the unsealed fluid side A are cut off while the surfaces ofthe ring body perpendicular to the circumferential direction thereofdefine gaps (in FIG. 2, a gap 27 which is formed by the distal endsurface 21 a of the convex part 21 and the opposite surface 24 a of theconcave part 24 opposing thereto, a gap 28 which is formed by the distalend surface of the convex part 23 and the opposite surface of theconcave part 22 opposing thereto, and a gap 29 on the inner peripheralside of the ring body) in the circumferential direction.

That is, the convex part 21 and the concave part 24 are constructed soas to come into sliding contact at a separation surface 25 concentricwith the second seal portion 3, and to come into sliding contact at aseparation surface 26 perpendicular to the axis of the seal ring. Thus,notwithstanding that the gaps 27, 28 and 29 as stated above are defined,any part of the seal surfaces of both the second seal portion 3 and thefirst seal portion 4 does not break off due to the separation portion 2.

Accordingly, even when the ring body has been thermally expanded tocause fluctuations in the intervals of the gaps 27, 28 and 29, the sealring can absorb the variations of dimensions in correspondence with thegaps while keeping a tightly enclosing state, and hence, it can maintaina tightly enclosing performance even against the change of an ambienttemperature.

Besides, in the seal ring 1 according to this embodiment, the first sealportion 4 is constructed of linear contact portions 41 which comes intolinear contact with the sidewall surfaces 72 of the annular groove 71.

In that region of the seal ring 1 which is not formed with theseparation portion 2, the linear contact portion 41 is constructed of anmountain shaped portion (protrusion) which is formed of an inclinationsurface 42 that inclines from the unsealed fluid side A in the secondseal portion 3, toward an inside diameter side (groove bottom side)being the side of the sidewall surface 72 of the annular groove 71, andan inclination surface 43 that inclines from the corner of the innerperipheral surface 5 of the seal ring 1 as lies on the unsealed fluidside A, toward an outside diameter side (opening side of the groove)being the side of the sidewall surface 72 of the annular groove 71.

Besides, at the convex part 21, the linear contact portion 41 isconstructed of an mountain shaped portion (protrusion) which is formedof an inclination surface 42 that inclines from the unsealed fluid sideA in the second seal portion 3, toward the groove bottom side being theside of the sidewall surface 72 of the annular groove 71, and aninclination surface 44 that is formed extending onto the outsidediameter side from the corner 47 of the separation surface 25 of theconvex part 21 as lies on the unsealed fluid side A, and that inclinesfrom the outside diameter side end of the end surface 48 of the convexpart 21 on the unsealed fluid side A, toward the outside diameter sidebeing the side of the sidewall surface 72 of the annular groove 71.

Besides, at the concave part 24, the linear contact portion 41 isconstructed of an mountain shaped portion (protrusion) which is formedof an inclination surface 45 that inclines from the corner 47 of theseparation surface 25 of the concave part 24 as lies on the unsealedfluid side A, toward the inside diameter side being the side of thesidewall surface 72 of the annular groove 71, and an inclination surface46 that inclines from the corner of the inner peripheral surface 5 ofthe concave part 24 as lies on the unsealed fluid side A, toward theoutside diameter side being the side of the sidewall surface 72 of theannular groove 71.

Here, for the brevity of description, the linear contact portion 41which is provided at the convex part 21 shall be described as a linearcontact portion 41 a, the linear contact portion 41 which is provided atthe concave part 24 shall be described as a linear contact portion 41 b,and the linear contact portion 41 which is provided in the region of theseal ring 1 which is not formed with the separation portion 2 shall bedescribed as a linear contact portion 41 c.

Besides, the linear contact portions 41 a, 41 b and 41 c arecontinuously provided in the first seal portion 4, and the linearcontact portions 41 a and 41 b are provided at a diametric distance inthe separation portion 2 as shown in the figures, whereby a leakage pathR (refer to FIG. 2) is formed between the linear contact portions 41 aand 41 b.

Here, the sectional shape of the linear contact portions in theseparation portion of the seal ring will be described with reference toFIG. 3.

Referring to FIG. 3, a is let denote the length between the linearcontact portions 41 a and 41 b in the diametric direction of the sealring, b the diametric length of the end surface 48 of the convex part 21on the unsealed fluid side A, c an axial length from the linear contactportion 41 to the end surface 48 of the convex part 21 on the unsealedfluid side A, S a sectional part which is determined by the dimensionsa, b and c, l a diametric length from the second seal portion 3 to thelinear contact portion 41 a (or linear contact portion 41 b), θ1 anangle which the inclination surface 43 defines to a plane perpendicularto the axis, and θ2 an angle which the inclination surface 42 defines tothe plane perpendicular to the axis.

Besides, the sectional part S which is determined by the dimensions a, band c is the diametric section of a space which is formed by the linearcontact portions 41 a and 41 b, the end surface 48 of the convex part 21on the unsealed fluid side A, and the sidewall surface 72 of the annulargroove 71. That is, the sectional part corresponds to the section of theleakage path which is formed owing to the fact that the linear contactportions 41 a and 41 b are provided at the diametric distance in theseparation portion 2. It is accordingly permitted to control thequantity of leakage, by appropriately adjusting the area of thesectional part S.

“Adjusting the area of the sectional part S” is to adjust the dimensionsa, b and c.

The dimensions a, b and c should desirably be smaller from the viewpointof reducing the quantity of leakage, but when they are excessivelysmall, any foreign matter existing in the sealed fluid becomes incapableof passing through the sectional part.

Accordingly, the dimensions b and c should suitably be 0.1-0.5 mm,preferably 0.15-0.3 mm. Besides, when the facility of the passing of theforeign matter and the reduction of the quantity of leakage areconsidered, it is desirable to make the dimensions b and c substantiallyequal.

Besides, the dimension a is made somewhat larger than the dimension b soas to taper the side surfaces of the leakage path, whereby thereleasability of a mold in a molding operation is made good.

Besides, the dimension l should desirably be small for reducing adragging torque which is caused by the relative rotation of the shaftand the seal ring, but when it is excessively small, the seal ring mightlie in the annular interspace between the shaft hole of the housing 80and the shaft 70 without contacting the sidewall surface 72 of theannular groove 71 at its linear contact portion 41. That is, it isapprehended that a gap will appear in the linear contact part betweenthe side surface of the seal ring and the sidewall surface 72 of theannular groove 71, so the quantity of leakage will increase.

Accordingly, in a case where H denotes the dimension of the insidediameter of the housing, where J denotes the dimension of the outsidediameter of the shaft, and where j=0.1 through 0.3 mm holds,l=H−J+jor so is suitable.

Also, it is apprehended that the seal ring will be twisted and deformedby the pressure of the sealed fluid. When the angles θ1 and θ2 of theside surface of the seal ring are excessively small, it is consideredthat a linear contact state will not be held in a case where the sealring has been twisted and deformed by the pressure of the sealed fluid.On the other hand, when the angles θ1 and θ2 of the side surface of theseal ring are excessively large, the cross-sectional area of the sealring decreases, and hence, the molding of the seal ring becomesdifficult.

Accordingly, the angles θ1 and θ2 should desirably be set at 5-20degrees.

Here, FIG. 5 is the enlarged view of the part C in FIG. 4, and thelinear contact portion 41 is enlarged therein. As shown in FIG. 5, thedistal end of the linear contact portion 41 has a predetermined width inthe diametric direction. The width ls should favorably be set at0.05-0.3 mm, preferably 0.1-0.2 mm, in consideration of the suppressionof the leakage quantity and the vomitability or eliminability of theforeign matter. Besides, both the ends of the linear contact portion 41should favorably be chamfered to R0.1 or less.

In this embodiment, as shown in FIGS. 1 and 2, the linear contactportions 41 are provided extending from that region of the seal ring 1which is not formed with the separation portion 2, to the concave part24, via a shift part 41 d at which the linear contact portion 41 c lyingon the outer peripheral side of the ring side surface shifts to thelinear contact portion 41 b lying on the inner peripheral side. However,the invention is not restricted to this aspect, but the linear contactportions 41 a and 41 b which are respectively provided at the convexpart 21 and the concave part 24 may continuously extend over the wholecircumference from the convex part 21 to the concave part 24, in a statewhere these linear contact portions 41 a and 41 b are not placed oneover the other on the circumference, that is, where they are spaced inthe diametric direction. The position and shape of the shift part, andthe existence or nonexistence of the shift part are not directlypertinent to the invention.

Besides, in this embodiment, the linear contact portions 41 arerespectively extended to the separation ends of the convex part 21 andthe concave part 24 in the circumferential direction, whereby the linearcontact portions 41 a and 41 b provided at the convex part 21 and theconcave part 24 are placed one over the other when projected in thediametric direction, but the invention is not restricted to this aspect.

More specifically, the linear contact portions need not be respectivelyextended to the separation ends in the circumferential direction at theconvex part 21 and the concave part 24, but the sectional part Sconstructing the leakage path may be formed in the sectional shape ofthe separation portion 2. Besides, even in a case where the linearcontact portions provided at the convex part 21 and the concave part 24are not placed one over the other when projected in the diametricdirection, the leakage path is formed as long as these linear contactportions are spaced in the diametric direction. Therefore, the sectionalpart S is supposed to be formed, and it is adjusted, whereby thequantity of leakage is controllable.

Here, in order to enhance the mold releasability, a flat surface M whichis flattened in the diametric direction may well be provided on theinner peripheral side as shown in FIGS. 6-8.

FIG. 6 is a plan view showing a seal ring 1A whose mold releasabilityhas been enhanced, FIG. 7 is a sectional view of the seal ring 1A takenalong 7-7 indicated in FIG. 6, and FIG. 8 is a sectional view of theseal ring 1A taken along 8-8 indicated in FIG. 6.

In releasing a mold, a releasing ejector pin is caused to abut againstthe flat surface M, whereby the ejector pin does not abut against anyinclination surface constituting the linear contact portion 41, andhence, the mold can be released without spoiling the shape of the sealring.

Besides, a resin composite which consists of a heat-resisting resin anda filler is applicable as a material which constructs the seal ring 1.

Here, mentioned as the heat-resisting resin is a resin which isexcellent in heat resistance, burning resistance and resistance tochemicals, and which exhibits an excellent mechanical property, forexample, a polycyanoaryl ether type resin (PEN), a polyether etherketone(PEEK) resin or the like aromatic polyether ketone resin, an aromatictype thermoplastic polyimide resin, a polyamide 4-6 type resin, apolyphenylene sulfide type resin, or a polytetrafluoroethylene typeresin.

Incidentally, the filler is compounded for the purposes of enhancing themechanical strength of the material, enhancing a wear-proofness,affording a low friction characteristic, etc., and it is not especiallyrestricted.

In the seal ring thus constructed, the first seal portion 4 is employedas the linear contact portions which come into linear contact with thesidewall surface 72 of the annular groove 71, so that the pressurereceiving area of the sliding portion can be decreased. Accordingly, theformation of the lubricating film by the lubricating oil can be madefavorable, and the reduction of the rotational sliding friction can beattained. Besides, even if the foreign matter has intruded into thesliding portion, it can be easily vomited.

Further, it is permitted to control the quantity of leakage inaccordance with the size of the gap which is formed owing to the factthat the linear contact portions are provided at the diametric distancein the separation portion.

The “size of the gap which is formed owing to the fact that the linearcontact portions are provided at the diametric distance in theseparation portion” signifies the sectional part S stated before, andthe quantity of leakage can be controlled by adjusting the dimensions a,b and c.

Further, the linear contact portions 41 a and 41 b respectively providedat the convex part 21 and the concave part 24 lie so as to be placed oneover the other when projected in the diametric direction, whereby thespace which is formed by these linear contact portions 41 a, 41 b, theend surface 48 of the convex part 21 on the unsealed fluid side A andthe sidewall surface 72 of the annular groove 71 becomes columnar, thatis, the leakage path R becomes columnar. Accordingly, the oil passingresistance of this region can be enlarged, so that the quantity ofleakage can be reduced still more.

Besides, the quantity of leakage can be controlled by adjusting thisregion, in other words, that length in the circumferential directionover which the linear contact portions 41 a and 41 b respectivelyprovided at the convex part 21 and the concave part 24 are placed oneover the other when projected in the diametric direction.

Also in a case where an equivalent leakage-path sectional area is setfor, for example, the seal ring 400 as shown in FIGS. 41 and 42 in theparagraph of the prior art, the quantity of leakage can be reduced stillmore.

Second Embodiment

A seal ring 1B according to the second embodiment of the presentinvention will be described with reference to FIG. 9-FIG. 12. FIG. 9 isa perspective view, partly broken away, showing the mounted state of theseal ring 1B according to this embodiment, FIG. 10 is a sectional viewof a separation portion (corresponding to the section 3-3 of the sealring 1 shown in FIG. 1), FIG. 11 is a sectional view corresponding tothe section 4-4 of the seal ring shown in FIG. 1, and FIG. 12 is anenlarged view of a part H in FIG. 11.

As compared with the seal ring 1 according to the first embodiment, thisembodiment consists in that the sectional shape of the seal ring is madesubstantially rectangular, and that the side surface of substantiallyrectangular section on the unsealed fluid side A is provided with linearcontact portions which come into linear contact with the sidewallsurface 72 of an annular groove 71. Incidentally, identical numerals andsigns are assigned to the same constituents as in the first embodiment,and they shall be omitted from description.

In the seal ring 1B according to this embodiment, a first seal portion 4is constructed of linear contact portions 41 which protrude from theside surface of the seal ring of substantially rectangular section onthe unsealed fluid side A, toward the sidewall surface 72 of the annulargroove 71, and which come into linear contact with the sidewall surface72.

In that region of the seal ring 1B which is not formed with theseparation portion 2, the linear contact portion 41 is constructed of anmountain shaped portion protruding toward the sidewall surface 72 of theannular groove 71, at the position of a length l on the inside diameterside of the seal ring from the corner of a second seal portion 3 on theunsealed fluid side A.

Besides, at a convex part 21, the linear contact portion 41 isconstructed of an mountain shaped portion which protrudes toward thesidewall surface 72 of the annular groove 71, at the position of thelength l on the inside diameter side from the corner of the second sealportion 3 on the unsealed fluid side A.

Besides, at a concave part 24, the linear contact portion 41 isconstructed of an mountain shaped portion which protrudes from theseparation surface 25 of the concave part 24 on the unsealed fluid sideA, and from the side surface of the seal ring on the unsealed fluid sideA.

Here, as in the first embodiment, the linear contact portion 41 which isprovided at the convex part 21 shall be described as a linear contactportion 41 a, the linear contact portion 41 which is provided at theconcave part 24 shall be described as a linear contact portion 41 b, andthe linear contact portion 41 which is provided in the region of theseal ring 1B which is not formed with the separation portion 2 shall bedescribed as a linear contact portion 41 c.

Besides, the linear contact portions 41 a, 41 b and 41 c arecontinuously provided in the first seal portion 4, and the linearcontact portions 41 a and 41 b are provided at a diametric distance inthe separation portion 2 as shown in the figures, whereby a leakage pathR (refer to FIG. 9) is formed between the linear contact portions 41 aand 41 b.

Here, the sectional shape of the linear contact portions in theseparation portion of the seal ring will be described with reference toFIG. 10.

Referring to FIG. 10, a is let denote the length between the linearcontact portions 41 a and 41 b in the diametric direction of the sealring, b the diametric length of an end surface 48 in the side surface ofthe convex part 21 on the unsealed fluid side A, from the corner 47 ofan end part in the inside diameter side of the seal ring, to the rise ofthe mountain shaped portion of the linear contact portion 41 a (boundarybetween the side surface and the mountain shaped portion), c an axiallength from the linear contact portion 41 to the end surface 48 of theconvex part 21 on the unsealed fluid side A, S a sectional part which isdetermined by the dimensions a, b and c, and l a diametric length fromthe second seal portion 3 to the linear contact portion 41 a (or linearcontact portion 41 c).

Besides, it is permitted to control the quantity of leakage, byappropriately adjusting the area of the sectional part S which isdetermined by the dimensions a, b and c.

“Adjusting the area of the sectional part S” is to adjust the dimensionsa, b and c. Here, the dimension a, dimension b, dimension c anddimension l are the same as in the first embodiment.

FIG. 12 is the enlarged view of the part H in FIG. 11, and the linearcontact portion 41 is enlarged therein. As shown in FIG. 12, the distalend of the linear contact portion 41 has a predetermined width in thediametric direction. The width ls should favorably be set at 0.05-0.3mm, preferably 0.1-0.2 mm, in consideration of the suppression of theleakage quantity and the vomitability or eliminability of the foreignmatter. Besides, both the ends of the linear contact portion 41 shouldfavorably be chamfered to R0.1 or less.

Besides, the angle β of the rise of the mountain shaped portionconstructing the linear contact portion 41 as measured from the sidesurface of the ring should suitably be 90 degrees<β<180 degrees,preferably 95 degrees<β<120 degrees in consideration of thereleasability of a mold.

As described above, according to this embodiment, the same advantages asin the first embodiment can be attained. Furthermore, since the linearcontact portions are provided on the side surfaces of the seal ring ofsubstantially rectangular section, the work of the mold becomes simpleand easy, and the mold releasability is enhanced without providing theflat surface of the first embodiment as shown in FIGS. 6-8.

EXAMPLE 1

A more practicable example will be described on the seal ring accordingto the first embodiment.

First, as a Comparative Example 1, there was used the seal ring 100 ofsubstantially rectangular section fabricated by injection molding withpolyether etherketone (PEEK) in which several sorts of fillers werecompounded (seal ring shown in FIGS. 34 and 35 as explained in theparagraph of the prior art).

Besides, in this example, the seal ring 100 molded as the ComparativeExample 1 was additionally worked to obtain the seal ring 1 shown inFIGS. 1-5 in the first embodiment.

Here, the dimensions of the individual parts of the seal ring 1 were setat seal-ring outside diameter=47.85 mm, seal-ring wall thickness 1.9 mm,seal-ring height 2 mm, l=0.6 mm, θ1=about 15 degrees, θ2=about 15degrees, b=0.25 mm, c=0.25 mm, and ls=0.2 mm.

Besides, as a Comparative Example 2, there was used a seal ring 400fabricated by additionally working the seal ring 100 molded as theComparative Example 1 (seal ring shown in FIGS. 38 and 39 as explainedin the paragraph of the prior art).

Incidentally, the seal-ring outside diameters, wall thicknesses andheights were equal in all of this example and the Comparative Examples 1and 2, and the separation portions (in the shape of daggers) were thespecial step cuts in all of this example and the Comparative Examples 1and 2.

Endurance tests were conducted using the three kinds of seal rings.

Conditions were set at an inflow oil temperature=80° C., oilpressure=1.3 MPa, rotational frequency of the shaft=4000 rpm, peripheralspeed=10 m/s, oil type=ATF, material of the side surface of theshaft=ADC12, material of the housing=S45C, and test time=144 hours. Asthe foreign matter, Testing dust type-7 (Kanto loam) stipulated in “JISZ 8901”, in amounts of 10 mg, was thrown into pipes located just infront of the mounted portions of the seal rings, at intervals of 24hours.

The results of the tests are indicated in Table 1. Incidentally, 1000cc/min=1 l/min holds.

TABLE 1 Maximum wear depth of Side Quantity of Quantity of surface ofleakage at leakage at Aluminum Start of Test End of Test shaft (μm)(cc/min) (cc/min) Remarks Example 3-4 130-140 130-140 Comparative 500-1400 10-20 Above 1000 Interrupted Example 1 in 30 hours due tolarge leakage quantity Comparative 2-4 300-400 300-400 Example 2

As indicated in Table 1, it has been verified that this example is muchless than the Comparative Example 1 in the wear depth of the aluminumshaft, and that, when compared with the Comparative Example 2, thisexample realizes a nearly equal wear depth of the aluminum shaft with aleakage quantity of half or less.

Third Embodiment

Now, a seal ring 1C according to the third embodiment of the presentinvention will be described.

In handling the seal ring, for example, in carrying the seal ring or inassembling the seal ring into the annular interspace between the twomembers, the seal ring sometimes suffers from a flaw such as strucktraces or pressed traces. Especially in the seal ring having theseparation portion, the ends of the separation portion might flaw.

FIG. 13 is a schematic view for explaining problems.

By way of example, in a case where the seal ring 1 according to thefirst embodiment has suffered from the flaw such as struck traces orpressed traces, at a part I shown in FIG. 13, any foreign matterexisting in the sealed fluid becomes easy to intrude between the linearcontact portions 41 a and 41 b from the part having flawed.

In the seal ring 1, the linear contact portions 41 a and 41 b areprovided at the diametric distance in the separation portion 2, wherebythe leakage path R is formed between these linear contact portions 41 aand 41 b. In a case where the direction of the leakage path R and therotational direction of the shaft have become identical, that is, wherethe sliding direction of the shaft relative to the seal ring is aJ-direction indicated in FIG. 13, the foreign matter existing in thesealed fluid becomes easily fed in between the linear contact portions41 a and 41 b.

Especially in a case where the shaft is made of the soft material andwhere the sliding direction of the shaft relative to the seal ring isthe J-direction indicated in FIG. 13, it is apprehended that the foreignmatter fed in between the linear contact portions 41 a and 41 b willintervene between the gap of the linear contact portions 41 a, 41 b ofthe seal ring 1 and the sidewall surface 72 of the annular groove 71 ofthe shaft 70, so the sidewall surface 72 will wear away drastically.

It is therefore favorable to construct the separation portion 2 of theseal ring 1 so that the leakage path R formed between the linear contactportions 41 a and 41 b may be in the reverse direction to the rotationaldirection of the shaft, in other words, that the sliding direction ofthe shaft 70 may become a K-direction indicated in FIG. 13. That is, theseal ring may be mounted so that the convex part 21 for sealing thesidewall surface 72 on the unsealed fluid side A may lie on a downstreamside in the sliding direction of the shaft 70.

Here, a plurality of seal rings are usually used in a set. It istherefore apprehended that the job of mounting the seal rings inaccordance with the rotational direction of the shaft will incur thelowering of a job efficiency.

This embodiment elucidates the seal ring 1C in which the separationportion of the seal ring 1 according to the first embodiment is endowedwith a directivity by providing a protrusive part as which the outerperipheral part of the separation portion 2 is protruded in thecircumferential direction relative to the inner peripheral part thereof,and a recessed part as which the outer peripheral part of the separationportion 2 is recessed in the circumferential direction relative to theinner peripheral part thereof and into which the protrusive part isfitted.

FIG. 14 is a perspective view, partly broken away, showing the mountedstate of the seal ring 1C according to the third embodiment of theinvention, while FIG. 15 is a perspective view, partly broken away,showing the spaced state of the separation portion in order to explainthe construction of the separation portion of the seal ring 1C accordingto this embodiment. Incidentally, identical numerals and signs areassigned to the same constituents as in the first embodiment, and theyshall be omitted from description.

A special step cut adopted in the separation portion 2 of the seal ring1C according to this embodiment includes the protrusive part 2 a aswhich one side of the separation portion 2 on the outer peripheral sideof the ring body of the seal ring is protruded in the circumferentialdirection relative to the inner-peripheral side end 2 c of the ringbody, and the recessed part 2 b as which the other side is recessedrelative to the inner-peripheral side end 2 c of the ring body and intowhich the protrusive part 2 a is fitted. Here, the protrusive part 2 aconstructs a first circularly-arcuate convex part, while the recessedpart 2 b constructs a first circularly-arcuate concave part.

Besides, as in the seal ring 1 according to the first embodiment, theprotrusive part 2 a includes a convex part 21 and a concave part 22 in awidthwise (axial direction) pair, and the recessed part 2 b includes aconcave part 24 and a convex part 23 in a widthwise pair. In addition,on the outer peripheral side of the seal ring 1C, the convex part 21 andthe concave part 24 are fitted, and the concave part 22 and the convexpart 23 are fitted. Here, the convex part 21 constructs a secondcircularly-arcuate convex part, while the concave part 24 constructs asecond circularly-arcuate concave part.

In the seal ring 1C according to this embodiment, a first seal portion 4is constructed of linear contact portions 41 which come into linearcontact with the sidewall surface 72 of the annular groove 71. This isthe same as in the seal ring 1, the linear contact portions 41 a, 41 band 41 c constructing the linear contact portions 41 are continuouslyprovided in the first seal portion 4, and the linear contact portions 41a and 41 b are provided at a diametric distance in the separationportion 2, whereby a leakage path R (refer to FIG. 14) is formed betweenthe linear contact portions 41 a and 41 b.

Here, the sectional shape of the linear contact portions in theseparation portion of the seal ring 1C is the same as in the seal ring1.

In this embodiment, accordingly, the same advantages as in the firstembodiment can be attained.

Besides, the feature of this embodiment is that, in mounting the sealring, the seal ring 1C is mounted into the annular groove 71 of theshaft 70 in correspondence with the rotational direction of this shaft70.

More specifically, the seal ring is disposed so that the protrusive part2 a may lie on the downstream side in the rotational direction of theshaft 70, and that the convex part 21 constructing the linear contactportion 41 at the protrusive part 2 a may lie on the side of thesidewall surface 72 of the annular groove 71 provided in the shaft 70 aslies on the unsealed fluid side A.

In this manner, the convex part 21 is located on the downstream side inthe rotational direction in the case where the shaft 70 rotates in theK-direction relative to the ring body as viewed in FIG. 14, whereby thedirection of the leakage path R between the linear contact portions 41 aand 41 b and the rotational direction of the shaft become reverse toeach other. The “fact that the direction of the leakage path R and therotational direction of the shaft are reverse to each other”, signifiesthat an opening formed by the linear contact portions 41 a and 41 b liesin the K-direction being the rotational direction of the shaft, on theinner peripheral side of the ring body.

Thus, even when the seal ring has been mounted in the state where itpartly suffers from the flaw such as struck traces or pressed traces, ata part I, the foreign matter existing in the sealed fluid is not fed inbetween the linear contact portions 41 a and 41 b by the rotation of theshaft.

Accordingly, the foreign matter can be prevented from interveningbetween the gap of the linear contact portions 41 a, 41 b of the sealring 1C and the sidewall surface 72 of the annular groove 71 of theshaft 70, and hence, it is permitted to prevent the sidewall surface 72from wearing away.

Further, in the separation portion 2 of the seal ring 1C, the protrusivepart 2 a and the recessed part 2 b which are respectively protrusive andrecessed relative to the inner-peripheral side end 2 c are provided onthe outer peripheral side of the ring body, whereby the separationportion is endowed with the directivity unlike the substantiallysymmetric shape as in the seal ring 1 according to the first embodiment,and the seal ring is permitted to be reliably mounted with theprotrusive part 2 a located on the downstream side in the rotationaldirection of the shaft.

Here, the convex part 21 protruded at the protrusive part 2 a shouldfavorably lie on the unsealed fluid side A. Since, however, the outerperipheral side of the ring body is protruded in this embodiment, thedirection of the leakage path R between the linear contact portions andthe rotational direction of the shaft become reverse to each other evenwhen the concave part 22 lies on the unsealed fluid side A, so that theprevention of the intrusion of the foreign matter and the prevention ofthe wear of the sidewall surface 72 are permitted.

Accordingly, the prevention of the intrusion of the foreign matter andthe prevention of the wear of the sidewall surface 72 are reliablypermitted by mounting the protrusive part 2 a on the downstream side inthe rotational direction of the shaft. Further, it is permitted toefficiently perform the mounting job of the seal ring in accordance withthe rotational direction of the shaft.

Here, as a dimensional difference in the circumferential direction islarger at the convex part 21 and the concave part 22 (or the concavepart 24 and the convex part 23 which are fitted therewith,respectively), that is, as the convex part 21 is more protrusive in thecircumferential direction, the quantity of leakage of a sealed fluid canbe made smaller. Since, however, this place is less influential on thequantity of leakage as compared with the sectional part S explained inthe first embodiment, the dimensional difference need not be especiallystipulated.

Also in the seal ring 1C, a flat surface M which is flattened in thediametric direction may be provided on the inner peripheral side as inthe seal ring 1A described with reference to FIGS. 6-8, whereby theenhancement of a mold releasability can be attained.

Fourth Embodiment

Now, a seal ring 1D according to the fourth embodiment of the presentinvention will be described.

FIG. 16 is a perspective view, partly broken away, showing the mountedstate of the seal ring 1D according to the fourth embodiment of theinvention, while FIG. 17 is a perspective view, partly broken away,showing the spaced state of a separation portion in order to explain theconstruction of the separation portion of the seal ring 1D according tothis embodiment. Incidentally, identical numerals and signs are assignedto the same constituents as in the foregoing embodiments, and they shallbe omitted from description.

As compared with the seal ring 1C according to the third embodiment,this embodiment consists in that the sectional shape of the seal ring ismade substantially rectangular as in the seal ring 1B described in thesecond embodiment, and that the side surface of the seal ring ofsubstantially rectangular section on the unsealed fluid side A isprovided with linear contact portions which come into linear contactwith the sidewall surface 72 of an annular groove 71.

That is, in the seal ring 1D according to this embodiment, the sectionalshape is substantially rectangular, and a protrusive part as which theouter peripheral side of the separation portion 2 is protruded in thecircumferential direction relative to the inner-peripheral side partthereof, and a recessed part as which the outer peripheral side of theseparation portion is recessed in the circumferential direction relativeto the inner-peripheral side part thereof and into which the protrusivepart is fitted, are provided as in the seal ring 1C according to thethird embodiment, whereby the separation portion of the seal ring 1Baccording to the second embodiment is endowed with a directivity.

EXAMPLE 2

A more practicable example will be described on the seal ring accordingto the third embodiment.

First, as a Comparative Example, the seal ring 1 shown in FIGS. 1-5 inthe first embodiment was obtained as in Example 1.

Besides, in this example, the seal ring 1C shown in FIGS. 14-15 in thethird embodiment was obtained by performing additional work afterinjection molding with polyether etherketone (PEEK) in which severalsorts of fillers were compounded.

Incidentally, the dimensions of the individual parts of the seal ringswere equal in both this example and the Comparative Example, and theywere the same as in Example 1.

Further, struck traces were inflicted on the part I indicated in FIG.14, in the seal ring of this example, while struck traces were inflictedon the part I indicated in FIG. 13, in the seal ring of the ComparativeExample.

Using the two kinds of seal rings, endurance tests were conducted by anendurance test equipment. Two samples were used in one time of test, andan oil pressure was fed between the samples.

FIG. 18 is a schematic view showing an example of the endurance testequipment.

The endurance test equipment 90 shown in FIG. 18 is provided with ahousing 91, and shafts 93 a and 93 b which are rotatably mounted on theinner periphery of the housing 91.

Ring slots 92 a and 92 b for mounting the seal ring samples S thereinare provided in the outer peripheries of the shafts 93 a and 93 b, aspace between the shafts 93 a and 93 b defines an oil chamber 94 intowhich testing oil is introduced, and the oil pressure is introduced froman oil-pressure introduction port 95 into the oil chamber 94.

Herein, when the oil pressure is applied with the seal ring samples Smounted in the ring slots 92 a and 92 b of the respective shafts 93 aand 93 b, the oil is tightly enclosed in a state where the ring sidesurfaces S1 of the respective seal ring samples S are pushed againstslot side surfaces 92 c and 92 d, and where the ring outer-peripheralsurfaces S2 thereof are pushed against the housing 91.

The results of the tests conducted under the same conditions as inExample 1 are indicated in Table 2.

TABLE 2 Maximum wear depth of Side Quantity of Quantity of Mountedsurface of leakage at leakage at Sliding position of Aluminum shaftStart of Test End of Test direction of Seal Ring (μm) (cc/min) (cc/min)Shaft Example Ring slot 202a 2 120 120 K-direction in FIG. 14 Ring slot202b 4 130 130 K-direction in FIG. 14 Comparative Ring slot 202a 150 140Above 1000 J-direction in Example FIG. 13 Ring slot 202b 2 140 140K-direction in FIG. 13

As indicated in Table 2, it has been verified that this example can makethe wear depth of the aluminum shaft much less than the ComparativeExample.

Fifth Embodiment

Now, a seal ring 1E according to the fifth embodiment of the presentinvention will be described.

During the use of a seal ring, it is apprehended that any foreign matterexisting in a sealed fluid will intrude into a separation portion 2.

FIG. 19 is a schematic view for explaining problems.

In a case where the foreign matter has intruded into the separationportion 2 in, for example, the seal ring 1 according to the firstembodiment, and where such a state continues, that is, where the foreignmatter has been bitten in the separation portion 2, a surface Q hatchedin FIG. 19B is pushed onto the sealed fluid side O by the foreignmatter, a state arises where the linear contact portion 41 b (a part Tindicated in FIG. 19A) does not lie in contact with a sidewall surface72. As a result, the foreign matter existing in the sealed fluid staysbetween the linear contact portion 41 b (the part T indicated in FIG.19A) and the sidewall surface 72, and it might cause the drawback ofwearing the sidewall surface 72, especially in a case where a shaft ismade of a soft metal. Besides, excessive wear might occur in the surfaceQ due to the foreign matter bitten in the separation portion 2.

This embodiment elucidates the seal ring 1E having a construction whichis difficult of biting the foreign matter and easy of vomiting theforeign matter even in the case where this foreign matter has intrudedinto the separation portion 2.

FIG. 20 is a perspective view, partly broken away, showing the mountedstate of the seal ring 1E according to the fifth embodiment of theinvention, FIG. 21 is a perspective view, partly broken away, showingthe spaced state of a separation portion in order to explain theconstruction of the separation portion of the seal ring 1E according tothis embodiment, FIG. 22 is a sectional view of the separation portion(corresponding to the section 3-3 of the seal ring shown in FIG. 1),FIG. 23 is a top view, partly broken away, showing the mounted state ofthe seal ring according to this embodiment, and FIG. 24 is an enlargedview of the part W of the seal ring as indicated in FIG. 23.Incidentally, identical numerals and signs are assigned to the sameconstituents as in the foregoing embodiments, and they shall be omittedfrom description.

As in the seal ring 1 according to the first embodiment, the seal ring1E according to this embodiment is formed with the stepped separationportion (special step cut), and it includes a convex part 21 and aconcave part 22 in a widthwise (axial direction) pair, on one side ofthe outer peripheral side of the seal ring through a separated part, anda concave part 24 and a convex part 23 in a widthwise pair, also on theother side. Besides, it is constructed so that the convex part 21 andthe concave part 24 may be fitted, while the concave part 22 and theconvex part 23 may be fitted. Here, the convex part 21 c constructs acircularly-arcuate convex part, and the concave part 24 constructs acircularly-arcuate concave part.

Here, the sectional shape of linear contact portions in the separationportion 2 of the seal ring 1E is shown in FIG. 22, and individualdimensions are the same as in the seal ring 1 (refer to FIG. 3).

In this embodiment, accordingly, the same advantages as in the firstembodiment can be attained.

Besides, the feature of this embodiment is that, at the convex parts 21and 23, separation surfaces 26 perpendicular to the axis of the sealring, among fitting surfaces at which the convex parts and the concaveparts are fitted, are respectively provided with protrusions which areprotrusive toward opposing surfaces and which come into linear contactwith the opposing surfaces.

As shown in FIGS. 20 and 21, at the convex part 21, the protrusion is alip part 26 b of substantially wedge-shaped section which has athickness gradually decreasing toward the side of the convex part 23 inthe axial direction, at a separation surface 26 a opposing to the convexpart 23 and being perpendicular to the axis. Besides, at the convex part23, the protrusion is a lip part 26 d of substantially wedge-shapedsection which has a thickness gradually decreasing toward the side ofthe convex part 21 in the axial direction, at a separation surface 26 copposing to the convex part 21 and being perpendicular to the axis.

Herein, the lip parts 26 b and 26 d are provided so that substantiallythe entire regions thereof may come into linear contact with therespectively opposing separation surfaces 26 c and 26 a in substantiallythe diametric direction of the seal ring. In a case where an oilpressure P has acted from the sealed fluid side O, the lip parts 26 band 26 d are respectively brought into pressed contact with theseparation surfaces 26 c and 26 a so as to come into linear sealingcontact.

Thus, even when the foreign matter has intruded into the separationportion 2, the separation surfaces 26 a and 26 c lie in linear contact,and hence, the foreign matter is not bitten between the separationsurfaces 26 a and 26 c. Even if the foreign matter has been bitten, itis bitten between the parts lying in linear contact, and hence, it iseasily vomited (a bite state is easily released).

Accordingly, even when the foreign matter existing in the sealed fluidhas entered the separation portion 2, it is not bitten in the separationportion 2, and the surface Q hatched in FIG. 19B, for example, is notpushed onto the sealed fluid side O by the foreign matter, so that thestate is not incurred where the linear contact portion 41 b (the part Tindicated in FIG. 19A) does not lie in contact with the sidewall surface72.

It is accordingly permitted to prevent the drawback that the foreignmatter stays between the linear contact portion 41 b and the sidewallsurface 72, thereby to wear this sidewall surface 72. Besides, since theforeign matter can be prevented from being bitten in the separationportion 2, the excessive wear can be prevented from appearing in each ofthe separation surfaces 26 a and 26 c (corresponding to the surface Qindicated in FIG. 19B).

Here in this embodiment, the protrusive height dimension d of each ofthe lip parts 26 b and 26 d is set at 0.15-0.2 mm. The dimension d isnot restricted to this value as long as it is set in consideration ofthe size of the foreign matter existing in the sealed fluid.

Besides, the angle θ3 (refer to FIG. 24A) of the distal end of each ofthe lip parts 26 b and 26 d should favorably be set at 20-120 degrees,preferably 60-90 degrees, in consideration of moldability anddurability.

The shape of the distal end of each of the lip parts 26 b and 26 d maybe an R shape, but in consideration of the workability of a mold, theshape may well be a substantially trapezoidal shape owing to theprovision of a flat part as shown in FIG. 24B. Angles θ4 and θ5 in thiscase should favorably be set at 90-180 degrees, preferably 95-120degrees, in consideration of the releasability of the mold. Thedimension f of the flat part should favorably be set at 0.1-0.5 mm,preferably 0.15-0.3 mm, in consideration of the workability of the moldand the vomitability or eliminability of the foreign matter.

Besides, a dimension e from the distal end of the convex part 21 or 23in the circumferential direction of the seal ring, to the correspondinglip part 26 b or 26 d in the circumferential direction, is notespecially restricted. In case of considering sealability, however, thedimension e should favorably be as small as possible, and it shouldfavorably be set at 0-1 mm, preferably 0-0.5 mm.

In the seal ring shown in FIGS. 20 and 21, the convex part 21 and theconcave part 23 are respectively provided with the protrusions, but thisaspect is not restrictive, and either the convex part 21 or the concavepart 23 may well be provided with the protrusion. FIGS. 25 and 26 show acase where the lip part 26 b is provided at only the convex part 21.

When the lip part is provided in one place, the bitten foreign matterdoes not stay between the lip parts, and the vomitability oreliminability of the foreign matter is enhanced more. Besides, in caseof considering assemblability, the lip part in one place is better.

Besides, in this embodiment, the separation surfaces 26 perpendicular tothe axis are respectively provided with the protrusions which areprotrusive toward the opposing surfaces, and which come into linearcontact with the opposing surfaces. However, separation surfaces 25concentric with the second seal portion 3 may well be provided withprotrusions which come into linear contact.

Also in the seal ring 1E, a flat surface M which is flattened in thediametric direction may be provided on the inner peripheral side as inthe seal ring 1A described with reference to FIGS. 6-8, whereby theenhancement of the mold releasability can be attained.

By the way, in the above, the seal ring which is formed with the steppedseparation portion (special step cut) as in the seal ring 1 according tothe first embodiment has been described, but this aspect is notrestrictive, and this embodiment is well suited for application to theseal ring which is formed with the stepped separation portion (specialstep cut) as in the seal ring 1C according to the third embodiment.

Sixth Embodiment

Now, a seal ring 1F according to the sixth embodiment of the presentinvention will be described.

FIG. 27 is a perspective view, partly broken away, showing the mountedstate of the seal ring 1F according to the sixth embodiment of theinvention, FIG. 28 is a perspective view, partly broken away, showingthe spaced state of a separation portion in order to explain theconstruction of the separation portion of the seal ring 1F according tothis embodiment, and FIG. 29 is a sectional view of the separationportion (corresponding to the section 3-3 of the seal ring shown in FIG.1). Incidentally, identical numerals and signs are assigned to the sameconstituents as in the foregoing embodiments, and they shall be omittedfrom description.

As compared with the seal ring 1E according to the fifth embodiment,this embodiment consists in that the sectional shape of the seal ring ismade substantially rectangular as in the seal ring 1B described in thesecond embodiment, and that the side surface of the seal ring ofsubstantially rectangular section on the unsealed fluid side A isprovided with linear contact portions which come into linear contactwith the sidewall surface 72 of an annular groove 71.

That is, the seal ring 1F according to this embodiment has thesubstantially rectangular sectional shape, and as in the seal ring 1Eaccording to the fifth embodiment, it is formed with the steppedseparation portion (special step cut), and it includes a convex part 21and a concave part 22 in a widthwise (axial direction) pair, on one sideof the outer peripheral side of the seal ring through a separated part,and a concave part 24 and a convex part 23 in a widthwise pair, also onthe other side. Besides, it is constructed so that the convex part 21and the concave part 24 may be fitted, while the concave part 22 and theconvex part 23 may be fitted.

Here, the sectional shape of linear contact portions in the separationportion 2 of the seal ring 1F is shown in FIG. 29, and individualdimensions are the same as in the seal ring 1B (refer to FIG. 11).

By the way, the seal ring which is formed with the stepped separationportion (special step cut) as in the seal ring 1B according to thesecond embodiment has been described in this embodiment, but this aspectis not restrictive, and this embodiment is well suited for applicationto the seal ring which is formed with the stepped separation portion(special step cut) as in the seal ring 1D according to the fourthembodiment.

EXAMPLE 3

A more practicable example will be described on the seal ring accordingto the sixth embodiment.

First, as a Comparative Example, there was used the seal ring 1B ofsubstantially rectangular section shown in FIGS. 9-12 in the secondembodiment and fabricated by injection molding with polyetheretherketone (PEEK) in which several sorts of fillers were compounded.

Besides, in this example, the seal ring molded as the ComparativeExample was additionally worked to obtain the seal ring 1F shown inFIGS. 27-29 in the sixth embodiment.

Here, the dimensions of the individual parts of the seal ring 1F wereset at seal-ring outside diameter=47.85 mm, seal-ring wall thickness=1.9mm, seal-ring height=2 mm, l=0.6 mm, β=about 116 degrees, b=0.2 mm,c=0.2 mm, ls=0.2 mm, d=0.2 mm, θ4=θ5=120 degrees, e=0.4 mm, and f=0.2mm.

Incidentally, the dimensions of the individual parts of the seal ringswere equal in both this example and the Comparative Example.

Using the two kinds of seal rings, endurance tests (wear accelerationtests) were conducted by an endurance test equipment.

In this example, the endurance test equipment 90 shown in FIG. 18 asexplained in Example 2 was employed.

Conditions were the same as in Examples 1 and 2. As a foreign matter,Testing dust type-7 (Kanto loam) stipulated in “JIS Z 8901”, in amountsof 10 mg, was thrown into pipes located just in front of the mountedportions of the seal rings, at intervals of 24 hours.

Further, in this example, the testing dust type-7 stipulated in “JIS Z8901”, in amounts of 1 mg, was applied as coatings between the fittingsurfaces, namely, separation surfaces 26 a and 26 c of the separationportions of the seal rings.

Two samples were used in one time of test, and an oil pressure was fedbetween the samples. Besides, 10 samples were tested for each of thisexample and the Comparative Example (that is, the number of times oftests was five).

In this example, wear depths became 10 μm or less in all of the 10samples, and the conspicuous wear of the side surface of an aluminumshaft was not observed. On the other hand, in the Comparative Example,wear depths were held at or below 10 μm in 8 of the 10 samples, butconspicuous wear appeared in the remaining 2 of the 10 samples.

Indicated in Table 3 are the test results of those 2 of the 10 samplesof this example in which the wear depths of the side surface of thealuminum shaft were large, and the test results of those 2 samples ofthe Comparative Example which exhibited the conspicuous wear.

TABLE 3 Maximum wear Quantity of Quantity of Mounted depth of Side sur-leakage at leakage at position of face of Aluminum Start of Test End ofTest Seal Ring shaft (μm) (cc/min) (cc/min) Example Ring slot 6 170 150202a Ring slot 5 160 150 202b Comparative Ring slot 54 160 240 Example202a Ring slot 46 150 250 202b

As indicated in Table 3, in this example, it is permitted to make thefrequency of wear appearance remarkably lower than in the ComparativeExample, and to attain the enhancement of the reproducibility of awear-proof performance.

Seventh Embodiment

A seal ring 1G according to the seventh embodiment of the presentinvention will be described with reference to FIG. 30-FIG. 33.

FIG. 30 is a plan view of the seal ring 1G according to the seventhembodiment of the invention, FIG. 31 is a perspective view, partlybroken away, showing the mounted state of the seal ring 1G according tothis embodiment, FIG. 32 is a sectional view of the seal ring 1G takenalong 32-32 as indicated in FIG. 30, and FIG. 33 is a sectional view ofthe seal ring taken along 33-33 as indicated in FIG. 30. Incidentally,identical numerals and signs are assigned to the same constituents as inthe foregoing embodiments, and they shall be omitted from description.

In each of the foregoing embodiments, the first seal portion 4 isconstructed of the linear contact portions 41 of single line as comeinto linear contact with the sidewall surface 72 of the annular groove71, but in this embodiment, it is constructed of linear contact portionsof two lines.

More specifically, in the seal ring 1G according to this embodiment, thefirst seal portion 4 is constructed of the linear contact portions oftwo lines (first linear contact portion 141 and second linear contactportion 142) as protrude from the side surface of the seal ring ofsubstantially rectangular section on the unsealed fluid side A, towardthe sidewall surface 72 of an annular groove 71, and as come into linearcontact with the sidewall surface 72.

The first linear contact portion 141 is provided continuously over thewhole circumference of the seal ring from a convex part 21 lying on oneside of a separation portion 2 (from a distal end surface 21 a or thevicinity of the distal end surface 21 a), to a concave part 24 lying onthe other side (to an opposing surface 24 a or the vicinity of theopposing surface 24 a).

Besides, the second linear contact portion 142 is provided continuouslyover the whole circumference from an end part 29 a which is provided onthe inside diameter side of the convex part 21 and which defines a gap29 on the inner peripheral side of the separation portion 2, or thevicinity of the end part (from one side of the separation portion 2), toan end part 29 b which is provided on the inside diameter side of theconcave part 24 and which defines the gap 29, or the vicinity of the endpart (to the other side of the separation portion 2).

Besides, as shown in FIG. 32, the first linear contact portion 141 isconstructed of an mountain shaped portion (protrusion) protruding towardthe sidewall surface 72 of the annular groove 71, at the position of alength l on the inside diameter side as viewed from the surface of asecond seal portion 3 on the unsealed fluid side A.

Besides, the second linear portion 142 is constructed of an mountainshaped portion (protrusion) protruding toward the sidewall surface 72 ofthe annular groove 71 similarly to the first linear contact portion 141,at the position of a length a on the inside diameter side as viewed fromthe first linear contact portion 141. Also, in this embodiment, thesecond linear contact portion 142 is provided at the concave part 24 soas to protrude from that side surface of the seal ring which is theseparation surface 25 of the concave part 24 on the unsealed fluid sideA.

Here, the first linear contact portion 141 and the second linear contactportion 142 are constructed without providing the shift part 41 dexplained in the foregoing embodiment (the part at which the linearcontact portion lying on the outer peripheral side shifts to the linearcontact portion lying on the inner peripheral side).

The first linear contact portion 141 and the second linear contactportion 142 are constructed in this manner, whereby the length of theparts of these linear contact portions traversing in the diametricdirection (the length of the parts lying in contact in the diametricdirection, within parts lying in contact with the sidewall surface 72 ofthe annular groove 71) can be decreased. It is therefore possible tolower the probability of the bite of any foreign matter into the linearcontact portions and the probability of the intrusion of the foreignmatter to that extent. Accordingly, the further stabilization of acontact state can be realized. Besides, it is more effective to disposethe first linear contact portion 141 and the second linear contactportion 142 substantially concentrically with a shaft 70.

The first linear contact portion 141 and the second linear contactportion 142 are disposed in this manner, whereby these linear contactportions 141 and 142 are spaced in the diametric direction in theseparation portion 2, and a leakage path R (refer to FIG. 31) is formedtherebetween.

Here, the sectional shape of the linear contact portions in theseparation portion 2 of the seal ring 1G will be explained withreference to FIG. 32. In a section shown in FIG. 32, the dimensionalrelations of the first linear contact portion 141 and the second linearcontact portion 142 to the body of the seal ring 1G are the same asthose of the linear contact portions 41 a and 41 b to the body of theseal ring 1B shown in FIG. 10.

In this embodiment, a sectional part S which is determined by dimensionsa, b and c is the diametric section of a space which is formed by thefirst linear contact portion 141 and second linear contact portion 142,the end surface 48 of the convex part 21 on the unsealed fluid side A,and the sidewall surface 72 of the annular groove 71. That is, thesectional part corresponds to the section of the leakage path R which isformed owing to the fact that the first linear contact portion 141 andthe second linear contact portion 142 are provided at a diametricdistance in the separation portion 2. It is accordingly permitted tocontrol the quantity of leakage, by appropriately adjusting the area ofthe sectional part S.

Besides, in this embodiment, a dimension (1+a) should desirably be smallfor reducing a dragging torque which is caused by the relative rotationof the shaft and the seal ring. However, when the dimension l isexcessively small, the seal ring might lie in the annular interspacebetween the shaft hole of a housing 80 and the shaft 70 withoutcontacting the sidewall surface 72 of the annular groove 71 at its firstlinear contact portion 141. That is, it is apprehended that a gap willappear in the linear contact part between the side surface of the sealring and the sidewall surface 72 of the annular groove 71, so thequantity of leakage will increase. Besides, making the dimension a smallleads to making the dimension b small, so that when the dimension a isexcessively small, the foreign matter is apprehended to be incapable ofpassing. Also the dimension l may be set at the same dimension as in theforegoing embodiments.

A part L shown in FIG. 33 corresponds to the first linear contactportion 141, and the sectional shape of this part becomes the same asthe sectional shape shown in FIG. 12. Besides, the sectional shape ofthe second linear contact portion 142 is the same shape.

As described above, according to this embodiment, the same advantages asin the second embodiment can be attained.

By the way, also in this embodiment, in the separation portion 2, thefirst linear contact portion 141 and the second linear contact portion142 may well be respectively extended to the end parts in thecircumferential direction, and they need not be extended so. Besides,the first linear contact portion 141 and the second linear contactportion 142 are provided so as to be placed one over the other whenprojected in the diametric direction, but the invention is notrestricted to this aspect.

Even in a case where, in the separation portion 2, the first linearcontact portion 141 and the second linear contact portion 142 are notplaced one over the other slightly when projected in the diametricdirection, the leakage path is formed owing to the fact that theselinear contact portions are respectively provided on the inside diameterside and outside diameter side of the seal ring. Therefore, thesectional part S is supposed to be formed, and it is adjusted, wherebythe quantity of leakage is controllable.

Besides, in a case where a degree to which the linear contact portionsare not placed one over the other when projected in the diametricdirection has become higher than in the above, the quantity of leakageis determined by a part which minimizes a sectional area that is formedby either of the end parts of the first linear contact portion 141 andthe second linear contact portion 142 on one side of the separationportion 2, either of the end parts of the first linear contact portion141 and the second linear contact portion 142 on the other side of theseparation portion 2, the side surface of the ring body (the end surface48 of the convex part 21 on the unsealed fluid side A), and the sidewallsurface 72 of the annular groove 71.

Besides, although the fourth and sixth embodiments have been describedas the modifications of the seal ring 1 according to the secondembodiment (the fourth and sixth embodiments have been described as themodifications of the seal ring according to the first embodiment), theshape as explained in the fourth and sixth embodiments is similarlyfavorable also in the seal ring 1G according to this embodiment. Thiscan be differently stated as that, in each of the respective seal rings1D and 1F according to the fourth and sixth embodiments, the first sealportion 4 is constructed of the first linear contact portion 141 andsecond linear contact portion 142 mentioned above, instead of the linearcontact portions 41.

More specifically, in the seal ring 1G, the protrusive part as which theouter-peripheral side part of the separation portion 2 is protruded inthe circumferential direction relative to the inner-peripheral side partthereof, and the recessed part as which the outer-peripheral side partof the separation portion is recessed in the circumferential directionrelative to the inner-peripheral side part thereof and into which theprotrusive part is fitted, are provided as in the seal ring 1C or 1D,whereby the separation portion of the seal ring 1G is endowed with adirectivity.

Besides, in the seal ring 1G, the convex parts 21 and 23 arerespectively provided with the protrusions which are protrusive towardthe opposing surfaces and which come into linear contact with theopposing surfaces, on the separation surfaces 26 perpendicular to theaxis, among the fitting surfaces where the convex part and the concavepart are fitted, as in the seal ring 1E or 1F, thereby to obtain theconstruction which is difficult of biting the foreign matter and easy ofvomiting the foreign matter even in the case where this foreign matterhas intruded into the separation portion 2.

EXAMPLE 4

Now, a more practicable example will be described.

There were employed the same seal rings as the Comparative Examples 1and 2 explained in Example 1.

Besides, as this example, the seal ring 1G shown in FIGS. 30-33 in thepreceding embodiment was obtained by injection molding with polyetheretherketone (PEEK) in which several sorts of fillers were compounded.

Here, the dimensions of the individual parts of the seal ring 1G,namely, the seal-ring outside diameter, the seal-ring wall thickness,the seal-ring height, etc. were set as in the seal ring 1F (1B) employedin Example 3.

Endurance tests were conducted using the three kinds of seal rings, andunder the same conditions as in Example 1. The results of the tests areindicated in Table 4.

TABLE 4 Maximum wear depth of Side Quantity of Quantity of surface ofleakage at leakage at Aluminum Start of Test End of Test shaft (μm)(cc/min) (cc/min) Remarks Example 2-4 130-140 130-140 Comparative 500-1400 10-20 Above 1000 Interrupted Example 1 in 30 hours due tolarge leakage quantity Comparative 2-4 300-400 300-400 Example 2

As indicated in Table 4, it has been verified that this example is muchless than the Comparative Example 1 in the wear depth of the aluminumshaft, and that, when compared with the Comparative Example 2, thisexample realizes a nearly equal wear depth of the aluminum shaft with aleakage quantity of half or less.

INDUSTRIAL APPLICABILITY

As described above, the present invention provides a seal ring ofexcellent quality which can attain reduction in the quantity of leakagewhile reducing rotational sliding friction, and which maintains a stablesealing performance over a long term.

1. A seal ring comprising: a first seal portion which seals a sidewallsurface of an annular groove on an unsealed fluid side of a shaft, theannular groove being provided in one of two members that areconcentrically assembled so as to be relatively rotatable; a second sealportion which seals a surface of the other of the two members, anannular interspace between the two members being sealed by the first andsecond seal portions, a ring body with a separation portion separated inone place in a circumferential direction to include a first end part anda second end part, said first seal portion being provided with linearcontact portions which come into linear contact with the sidewallsurface of the annular groove on the unsealed fluid side, so as toextend continuously over a whole circumference of the seal ring from oneside of said separation portion to the other side thereof, and saidlinear contact portion which is provided on one side of said separationportion, and said linear contact portion which is provided on the otherside of said separation portion being located at a distance in a radialdirection of the seal ring so that an inner circumferential surface ofthe first end part on one side of the separation portion comes intocontact with an outer circumferential surface of the second end part onthe other side of the separation portion and said linear contactportions having a narrower width in the radial direction than adjacentparts of the ring body to control a quantity of leakage from a sealedfluid side to the unsealed fluid side of the shaft; and wherein saidlinear contact portions include: a first linear contact portion which isextended continuously from one side of said separation portion to theother side thereof, and which comes into linear contact with thesidewall surface of the annular groove on the unsealed fluid side; and asecond linear contact portion which lies nearer a groove bottom side ofthe annular groove than said first linear contact portion, which isextended continuously from one side of said separation portion to theother side thereof, and which comes into linear contact with thesidewall surface of the annular groove on the unsealed fluid side, saidlinear contact portion provided on one side of said separation portionis said first linear contact portion, while said linear contact portionprovided on the other side of said separation portion is said secondlinear contact portion.
 2. The seal ring as defined in claim 1, whereina quantity of leakage is adjusted by a size of a sectional area of asection of a space in the radial direction, the space being formed bysaid linear contact portion provided on one side of said separationportion, said linear contact portion provided on the other side of saidseparation portion, a part of the ring body lying between said linearcontact portion provided on one side and said linear contact portionprovided on the other side, and the sidewall surface of the annulargroove is on the unsealed fluid side.
 3. The seal ring as defined inclaim 1, wherein said linear contact portions define protruding portionswhich protrude from a side surface of the ring body, toward the sidewallsurface of the annular groove on the unsealed fluid side.
 4. The sealring as defined in claim 1, wherein said linear contact portion providedon one side of said separation portion is located nearer a side of saidother member than said linear contact portion provided on the other sideof said separation portion.
 5. The seal ring as defined in claim 4,wherein on the other member side of the ring body, the separation endpart of said one side which is provided with said linear contact portionis provided with a first circularly-arcuate protrusive part whichprotrudes in the circumferential direction, while the separation endpart of said other side is provided with a first circularly-arcuaterecessed part which is fitted with said first circularly-arcuateprotrusive part, and said first circularly-arcuate protrusive part isprovided with a second circularly-arcuate part which protrudes in thecircumferential direction, while said first circularly-arcuate recessedpart is provided with a second circularly-arcuate recessed part which isfitted with said second circularly-arcuate protrusive part.
 6. The sealring defined in claim 5, wherein one of respective fitting surfaces atwhich said second circularly-arcuate protrusive part and secondcircularly-arcuate recessed part are fitted is provided with aprotrusion which comes into linear contact with the other fittingsurface.
 7. The seal ring as defined in claim 1, wherein the separationend part of said one side of said separation portion is provided with acircularly-arcuate protrusive part which protrudes in thecircumferential direction, while the separation end part of said otherside of said separation portion is provided with a circularly-arcuaterecessed part which is fitted with said circularly-arcuate protrusivepart, and one of respective fitting surfaces at which saidcircularly-arcuate protrusive part and said circularly-arcuate recessedpart are fitted is provided with a protrusion which comes into linearcontact with the other fitting surface.
 8. The seal ring as defined inclaim 7, wherein the fitting surfaces are surfaces which are radiallyspaced from an axis of said seal ring, and which extend in thecircumferential direction.
 9. A seal ring comprising: a first sealportion which seals a sidewall surface of an annular groove on anunsealed fluid side of a shaft, the annular groove being provided in oneof two members that are concentrically assembled so as to be relativelyrotatable; and a second seal portion which seals a surface of the otherof the two members, an annular interspace between the two members beingsealed by the first and second seal portions, a ring body with aseparation portion separated in one place in a circumferential directionto include a first end part and a second end part, said first sealportion being provided with linear contact portions which come intolinear contact with the sidewall surface of the annular groove on theunsealed fluid side, so as to extend continuously over a wholecircumference of the seal ring from one side of said separation portionto the other side thereof, said first and second end parts of the ringbody having abutting parts which abut each other in a radial directionof the seal ring, said linear contact portions having adjacent parts oneof which is provided on said abutting part of said first end of the ringbody and the other of which is provided on said abutting part of saidsecond end part of the ring body, said adjacent parts being located at adistance in the radial direction of the seal ring so that a gap isformed therebetween, and a quantity of leakage from a sealed fluid sideto the unsealed fluid side of the shaft being controlled by a spacedefined by said abutting parts, said adjacent parts, and the sidewallsurface of the annular groove.
 10. The seal ring as defined in claim 9,wherein a first portion of said linear contact portion is provided onone side of said separation portion, and a second portion of said linearcontact portion is provided on the other side of said separation portionand said first and second portions have regions which are placed oneover the other when said linear contact portions are projected in theradial direction.
 11. The seal ring as defined in claim 9, wherein aquantity of leakage is adjusted by a size of a sectional area of asection of a space in the radial direction, the space being formed bysaid linear contact portion provided on one side of said separationportion, said linear contact portion provided on the other side of saidseparation portion, a part of the ring body lying between said linearcontact portion provided on one side and said linear contact portionprovided on the other side, and the sidewall surface of the annulargroove is on the unsealed fluid side.
 12. The seal ring as defined inclaim 9, wherein said linear contact portions define protruding portionswhich protrude from a side surface of the ring body, toward the sidewallsurface of the annular groove on the unsealed fluid side.
 13. The sealring as defined in claim 9, wherein said linear contact portion providedon one side of said separation portion is located nearer a side of saidother member than said linear contact portion provided on the other sideof said separation portion.
 14. The seal ring as defined in claim 13,wherein on the other member side of the ring body, the separation endpart of said one side which is provided with said linear contact portionis provided with a first circularly-arcuate protrusive part whichprotrudes in the circumferential direction, while the separation endpart of said other side is provided with a first circularly-arcuaterecessed part which is fitted with said first circularly-arcuateprotrusive part, and said first circularly-arcuate protrusive part isprovided with a second circularly-arcuate part which protrudes in thecircumferential direction, while said first circularly-arcuate recessedpart is provided with a second circularly-arcuate recessed part which isfitted with said second circularly-arcuate protrusive part.
 15. The sealring defined in claim 14, wherein one of respective fitting surfaces atwhich said second circularly-arcuate protrusive part and secondcircularly-arcuate recessed part are fitted is provided with aprotrusion which comes into linear contact with the other fittingsurface.
 16. The seal ring as defined in claim 9, wherein the separationend part of said one side of said separation portion is provided with acircularly-arcuate protrusive part which protrudes in thecircumferential direction, while the separation end part of said otherside of said separation portion is provided with a circularly-arcuaterecessed part which is fitted with said circularly-arcuate protrusivepart, and one of respective fitting surfaces at which saidcircularly-arcuate protrusive part and said circularly-arcuate recessedpart are fitted is provided with a protrusion which comes into linearcontact with the other fitting surface.
 17. The seal ring as defined inclaim 16, wherein the fitting surfaces are surfaces which are radiallyspaced from an axis of said seal ring, and which extend in thecircumferential direction.
 18. The seal ring as defined in claim 9,wherein said linear contact portions include: a first linear contactportion which is extended continuously from one side of said separationportion to the other side thereof, and which comes into linear contactwith the sidewall surface of the annular groove on the unsealed fluidside; and a second linear contact portion which lies nearer a groovebottom side of the annular groove than said first linear contactportion, which is extended continuously from one side of said separationportion to the other side thereof, and which comes into linear contactwith the sidewall surface of the annular groove on the unsealed fluidside, said linear contact portion provided on one side of saidseparation portion is said first linear contact portion, while saidlinear contact portion provided on the other side of said separationportion is said second linear contact portion.